1. Field of Invention
The present invention relates to an organic light-emitting display (OLED) device and fabricating method thereof. More particularly, the present invention relates to a top emission active matrix OLED device and fabricating method thereof.
2. Description of Related Art
Organic light-emitting display (OLED) is a highly efficient electrical-to-photonic conversion device. Common applications of the OLED include indicator light, display panel and the light-emitting portion of an optical read/write head. Because OLED devices have special properties including no viewing angle restrictions, easy to fabricate, low production cost, high response, wide operating temperature range and full coloration, the OLED device is the preferred display for most multi-media systems.
At present, one particular type of OLED device called an active matrix OLED device is in active research. The active matrix OLED is formed, for example, by depositing an organic light-emitting layer and a cathode layer over a substrate with a thin film transistor array thereon. The thin film transistors are used for driving the light-emitting units inside the active matrix OLED device.
In general, an active matrix OLED device is a bottom emission device. Since the anode layer of the active matrix OLED device is made from a transparent material and the cathode layer is made from non-transparent metallic material, light produced by the organic light-emitting layer will emit from the bottom portion of the device. For this type of device, the gate of the thin film transistors is capable of blocking external light from getting into the channel layer through the backside of the substrate to cause photoelectric current leakage. Furthermore, to prevent light produced by the organic light-emitting layer from reaching the channel layer of the thin film transistors, the anode layer of the active matrix OLED device must be properly positioned with respect to the thin film transistor. In other words, the anode layer must not be positioned over the thin film transistors. Hence, the extent of the light-emitting area in each pixel structure is severely restricted.
However, even if the anode layer is not patterned over the thin film transistor, light produced by the organic light-emitting layer can still scatter into the channel layer leading to a photoelectric leakage current.
The aforementioned photoelectric leakage current often leads to a drift in the device's operating current. Ultimately, the gray scale of the device is affected, thus leading to a lower contrast. Moreover, the photoelectric leakage also causes the operating current of the device to increase with time. Consequently, not only is the working life of the device reduced, but the power consumption is correspondingly increased.